Sheet composition for pipe connection, and sheet for electrofoaming fusion and connecting apparatus for underground pipes using the sheet composition

Abstract

The present invention relates to a connecting apparatus used for connecting underground pipes and to a composition for preparing a foamed sheet for the same. Specifically, the present invention relates to a sheet composition for pipe connection which comprises 1 to 10 parts by weight of a masterbatch including low-density polyethylene, high-density polyethylene, a maleic anhydride graft copolymer, a metallocene polyethylene elastomer, a foaming agent, and an additive, based on 100 parts by weight of a base resin including low-density polyethylene, high-density polyethylene, a maleic anhydride graft copolymer, and a metallocene polyethylene elastomer. When using the composition according to the present invention, a non-foamed sheet is produced during melt extrusion, and a foamed sheet is obtained at a high temperature by laminating the non-foamed sheet with a heater line and applying electricity thereto. Therefore, the sheet composition can be fused and filled into a pipe.

The invention claimed is: 
     
       1. A sheet composition for pipe connection comprising:
 1 to 10 parts by weight of a master batch comprising 30 to 50% by weight of low-density polyethylene, 5 to 20% by weight of high-density polyethylene, 10 to 30% by weight of a metallocene polyethylene-based elastomer, 20 to 40% by weight of a maleic anhydride graft copolymer, 1 to 10% by weight of a foaming agent and 0.1 to 5% by weight of an additive, with respect to 100 parts by weight of a base resin comprising 30 to 50% by weight of low-density polyethylene, 5 to 20% by weight of high-density polyethylene, 10 to 30% by weight of metallocene polyethylene-based elastomer, and 20 to 40% by weight of maleic anhydride graft copolymer. 
 
     
     
       2. The sheet composition for pipe connection according to  claim 1 , wherein the low-density polyethylene has a melt index (MI) of 2 to 4 g/10 min (190, 2.16 kg), the high-density polyethylene has a melt index (MI) of 20 to 30 g/10 min (190, 2.16 kg), the metallocene polyethylene-based elastomer has a melt index (MI) of 1 to 5 g/10 min (190, 2.16 kg), and the maleic anhydride graft copolymer has a melt index (MI) of 0.7 to 3.5 g/10 min (190, 2.16 kg). 
     
     
       3. The sheet composition for pipe connection according to  claim 1 , wherein the additive is one selected from a lubricant, a pigment, an antioxidant, a UV stabilizer, a filler or a mixture thereof. 
     
     
       4. The sheet composition for pipe connection according to  claim 2 , wherein the lubricant is one selected from calcium stearate, zinc stearate, magnesium stearate, aluminum stearate, glycerin stearate, butyl stearate, solid paraffin, liquid paraffin, or a mixture thereof. 
     
     
       5. The sheet composition for pipe connection according to  claim 1 , wherein the foaming agent is one selected from azodicarbonamide (ADCA), azodiisobutyronitrile (ABBN), dinitrosopentamethylenetetramine (DNPT), para-toluenesulfonyl hydrazide (TSH) and oxybis benzenesulfonyl hydrazide (OBSH), or a mixture thereof. 
     
     
       6. The sheet composition for pipe connection according to  claim 1 , wherein the base resin further comprises 0.1 to 10% by weight of a vinyl acetate-based resin containing 5 to 30% by weight of vinyl acetate. 
     
     
       7. The sheet composition for pipe connection according to  claim 6 , wherein the vinyl acetate-based resin is an ethylene-vinyl acetate copolymer. 
     
     
       8. The sheet composition for pipe connection according to  claim 1 , wherein the foaming sheet composition for pipe connection has a foaming temperature of 165 to 195. 
     
     
       9. A method for producing a sheet for electrofoaming fusion using the sheet composition, comprising:
 a) weaving a heater line having a zigzag or net shape using a raschel machine; 
 b) incorporating a master batch comprising 30 to 50% by weight of low-density polyethylene, 5 to 20% by weight of high-density polyethylene, 10 to 30% by weight of a metallocene polyethylene-based elastomer, 20 to 40% by weight of a maleic anhydride graft copolymer, 1 to 10% by weight of a foaming agent and 0.1 to 5% by weight of an additive, with respect to 100 parts by weight of a base resin comprising 30 to 50% by weight of low-density polyethylene, 5 to 20% by weight of high-density polyethylene, 10 to 30% by weight of a metallocene polyethylene-based elastomer, and 20 to 40% by weight of a maleic anhydride graft copolymer, into an extruding machine, and melt-extruding the master batch at a foaming temperature or less to produce a non-foamed sheet; and 
 c) laminating the extruded non-foamed sheet on one or both surfaces of the woven heater line, followed by pressing to integrate the non-foamed sheet with the heater line. 
 
     
     
       10. The method according to  claim 9 , further comprising: a temperature sensor provided between the heater line and the non-foamed sheet. 
     
     
       11. The method according to  claim 10 , wherein the heater line is coated with a glass fiber. 
     
     
       12. A sheet for electrofoaming fusion produced by the production method according to  claim 9 , and heated and foamed when current is applied to the heater line. 
     
     
       13. A sheet for electrofoaming fusion comprising:
 a heater line having a zigzag or net shape; 
 a non-foamed sheet laminated to one or both surfaces of the heater line and obtained by melt-extruding the composition according to  claim 1  at a foaming temperature or less; and 
 a temperature sensor provided between the heater line and the non-foamed sheet. 
 
     
     
       14. A connecting apparatus of underground pipes comprising:
 the sheet for electrofoaming fusion according to  claim 13 ; 
 a polyethylene support sheet that surrounds the outer surface of the sheet for electrofoaming fusion, is fused to the sheet for electrofoaming fusion and supports a connection portion of the sewer pipes; and 
 a fastening band that adheres the sheet for electrofoaming fusion and the support sheet to the polyethylene sewer pipes, supports the sheet for electrofoaming fusion and the support sheet during foaming and fusion, and hermetically seals the gap of the pipe connection portion or the sheet overlapping portion. 
 
     
     
       15. The connecting apparatus according to  claim 14 , wherein the fastening band is of a band clamp-type.